Dinochelus ausubeli, Ahyong & Chan & Bouchet, 2010

Ahyong, Shane T., Chan, Tin-Yam & Bouchet, Philippe, 2010, Mighty claws: a new genus and species of lobster from the Philippine deep sea (Crustacea, Decapoda, Nephropidae), Zoosystema 32 (3), pp. 525-535 : 529-534

Dinochelus ausubeli n. sp.

( Figs 2 A-I; 3; 4; Table 1)

Thaumastochelopsis sp. – Anonymous 2008: 4. — Crist et al. 2009: 44.

HOLOTYPE. — Philippines. AURORA stn CP2748, 15°56’N, 121°45’E, 249- 247 m, 2.VI.2007,š, cl 31.1 mm, pcl 26.1 mm (NMCR).

ETYMOLOGY. — Named in honour of Jesse Ausubel, patron of the Census of Marine Life, in recognition of his vision and support for marine biodiversity exploration.

DISTRIBUTION. — Presently known only from the type locality.

DIAGNOSIS. — Eyes well developed, movable, cornea present. Surfaces and margins of pleura 2-5 with laterally minute granules or spinules. Major and minor pereopod 1 palms with numerous spinules; pollex and dactylus with occlusal margins bearing 2 divergent rows of spines. Pereopod 1 minor chela fingers 3 times as long as palm. Uropodal exopod proximal segment with spinose outer margin; distal segment wider than half width of proximal segment.

DESCRIPTION

Rostrum triangular, without dorsal median groove; surface and margins setose, setae extending posteriorly onto carapace surface on either side of midline to level of cervical groove; apex acute; deflected ventrally; finely and sparsely setose; margins with 3 spines, inclined anterodorsally.

Carapace surface with scattered spinules or acute granules, otherwise smooth, without median groove or carina; with small supraorbital spine; orbital fossa obsolete; pterygostomial margin faintly convex, with prominent antennal spine; anterolateral angle rounded, with few small spines or denticles, meeting pterygostomial margin at acute angle; postcervical, cervical, hepatic and antennal grooves continuous with each other; postcervical groove deep, crossing dorsum; branchiocardiac groove faintly indicated, posterior half subparallel to midline; marginal carina distinct. Lower and posterior margins setose.

Abdomen strongly depressed; smooth dorsally. Tergite 1 short, with transverse row of spinules on either side of midline; pleuron rudimentary, with 2 spinules on posterior surface; with 2 small, ventrally directed spines adjacent to pleopod articulation. Tergites 1-5 smooth dorsally, posterior margins unarmed, setose; lateral carinae granulate or minutely spinulate; pleural surfaces with minute spines, margins rounded to subtruncate, setose, posterolaterally with few spinules or granules. Tergite 6 smooth dorsally except for irregular row of minute spinules along midline of posterior half; posterior margin minutely spinulate, medially emarginate; lateral carina spinulate; pleural surface sparsely spinulate and granulate; lower pleural margin broadly rounded, setose, unarmed. Telson subquadrate; lateral sinuous, widest in anterior half; posterior margin broadly rounded; surface sparsely granulate or minutely spinulate.

Antennular peduncle overreaching rostrum by half length of distal peduncular article; inner flagellum longest, 0.95 pcl; outer flagellum thicker, setose ventrally.Antennal basal article wider than one-third epistome width, surrounded by wide band of arthrodial membrane;basicerite with stout distodorsal spine reaching midlength of scaphocerite, ventral surface with few scattered spinules. Scaphocerite narrowly triangular, length about 3 times width; outer margin unarmed; inner margin with 8 or 9 spines.

Epistome fused anteriorly with carapace; inverted T-shaped, with narrow median portion and slen- der, transverse posterior portion; margins curved, spinulate; anterior surface with 2 spinules at base of antennular articulation; posterior margin raised, with row of granules.

Eyestalk movable; corneal region rounded, unpigmented, sparsely setose dorsally; not extending beyond antennular peduncle segment 2.

Mouthparts examined in situ, not dissected. Mandible robust; palp 3-segmented.Maxilliped 2 exopod reaching beyond merus; flagellum absent; epipod absent. Maxilliped 3 exopod reaching midlength of ischium, flagellum multiarticulate, reaching proximal quarter of merus; epipod with well-developed podobranch; with 2 arthrobranchs.

Pereopods 1-4 with epipod and podobranch. Pereopod 5 without epipod or podobranch.

Pereopod 1 chelate, with few sparse setae; left and right markedly unequal and dissimilar; coxae with inner distal spine and 2 inner proximal spinules.

Major pereopod 1 ischium with spinulate inner margin; merus with 4 small spines on inner proximal margin and distal spine on outer margin; carpus with spine on outer ventral margin; propodus palm glabrous, dorsolateral and distomesial surface sparsely spinulose; dactylus and pollex about 4 times as long as palm; occlusal margins of pollex and dactylus lined with longer spines approximately evenly interspersed between several shorter spines, spines oriented obliquely to main axis of pollex and dactylus, alternately inclined to right and left forming two divergent rows, spines of dactylus and pollex interlocking when occluded; non-occlusal margins of pollex and dactylus smooth; dactylus with spine anterior to each articular condyle.

Minor pereopod 1 ischium with spines along inner margin; merus with row of spines along proximal three-fourths and 1 spine on outer distal margin; carpus with spine on outer distal margin; propodus palm with outer and lower surface bearing numerous spines extending onto proximal half of pollex; dactylus and pollex about 3 times as long as palm; dactylus outer margin with row of 8 well-spaced spines; spines of occlusal margins of pollex and dactylus orientation similar to that of major cheliped.

Pereopod 2 chelate, with few sparse setae; coxa with small inner distal spine and spinule on inner margin; basis flexor margin with cluster of spinules; ischium with spinose flexor margin; merus, carpus and propodus unarmed; pollex and dactylus with finely serrate occlusal margins, length about as long as palm.

Pereopod 3 chelate; coxa with 2 distal spines on inner margin; basis and ischium with few spinules on flexor margin; merus, carpus and propodus unarmed; pollex and dactylus with finely serrate occlusal margins, length almost as long as palm.

Pereopod 4 non-chelate; coxa with 1 or 2 inner distal spines; basis, ischium, merus, carpus, propodus and dactylus unarmed; dactylus densely setose.

Pereopod 5 chelate; coxa unarmed on inner margin; basis, ischium, merus, carpus and propodus unarmed; dactylus slightly expanded distally, setose dorsally; pollex and dactylus with stiff, obliquely directed setae on occlusal margins.

Pleopod 1 with distal and proximal segments articulating, forming copulatory organ. Proximal segment sparsely setose on inner distal margin. Distal segment slightly arcuate, tapering distally to rounded apex; slightly cannulate medially, flattened distally; glabrous.

Pleopod 2 biramous; basis inner distal margin setose; exopod and endopod elongate-ovate with setose margins; endopod longer than exopod, with appendix masculina.

Pleopods 3-5 biramous; basis inner distal margin setose; exopod and endopod elongate-ovate with setose margins; endopod longer than exopod, with slight basal swelling.

Uropodal protopod short, stout, with anterior spine overhanging exopod articulation; with denticulate lobe overhanging endopod articulation. Exopod proximal segment broadly trianguloid; outer margin irregularly spinose; distal margin curved, lined with setae and row of graded spines (largest laterally) above distal segment; distal segment wide, short, distal margin unarmed, rounded, demarcated from proximal segment by submarginal diaeresis. Endopod markedly smaller than exopod, with posterior margin lined with 11-13 spines.

Colour in life ( Fig. 4 )

Overall translucent white (including cornea) with central third diffusely reddish-pink. Abdominal somites and tailfan with diffuse reddish-pink patches and blotches. Antennular and antennal flagella, and pereopod 1 chelae reddish-pink. Pereopods 2-5 white.

REMARKS

Species of Dinochelus n. gen., Thaumastocheles and Thaumastochelopsis , are superficially very similar, and apart from eye, uropod and maxilliped form, differ most prominently in major cheliped armature. Specimens collected by trawl or dredge are very often damaged, and in the case of incomplete specimens, or where only a major cheliped is collected, D. ausubeli n. gen., n. sp. is nevertheless identifiable. Of the known thaumastocheliform nephropids, the first chelipeds of D. ausubeli n. gen., n. sp. are most similar to those of Thaumastocheles zaleucus from the Caribbean Sea, in which the occlusal margins of the fingers are lined with two divergent rows of spines. The chelipeds of D. ausubeli n. gen., n. sp., however, differ from those of T. zaleucus in having distinctly spinose palms (versus at most a few scattered spinules), and the fingers of the minor pereopod 1 are proportionally longer, being three times, versus less than twice the palm length. The cheliped armature of D. ausubeli n. gen., n. sp. differs from other species of Thaumastocheles and species of Thaumastochelopsis in having two divergent rows of slender spines on the occlusal margins of the fingers, rather than a single row of either upright spines or low, triangular serrations. It should be noted that a species recently described from Madagascar, Thaumastochelopsis plantei Burukovsky, 2005 , is actually an axiidean of the genus Ctenocheles Kishinouye, 1926 (see also Tshudy & Sorhannus 2000). Thus, only two species of Thaumastochelopsis (i.e. T. wardi and T. brucei ) are presently known.

Figures

FIG. 2. — A-I, Dinochelus ausubeli n. gen., n. sp., š holotype, pcl 26.1 mm (NMCR); J, K, Thaumastochelopsis brucei Ahyong, Chu & Chan,2007,š holotype,pcl 21.1 mm (AM P49083);A, body,right lateral view;B, J, anterior carapace,dorsal view;C, abdomen,dorsal view; D, right uropodal exopod, ventral view; E, right antenna, dorsal view; F, right antenna, ventral view; G, K, epistome,ventral view; H, right maxilliped 2, lateral view; I, right maxilliped 3, lateral view. Scale bar: A-D, G, 10.0 mm; E, F, H, I, 5.0 mm; J, K, 7.5 mm.

FIG. 4. — Dinochelus ausubeli n. gen., n. sp., š holotype, pcl 26.1 mm (NMCR),abdomen slightly damaged and causing the posterior part of abdomen to bend right: A, left lateral view; B, dorsal view.